JPH066420Y2 - Flat cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a flat cable used as a signal cable for a computer, for example.

[Prior Art] A conventional flat cable 1 is, as shown in FIG.
The flat insulating sheath 2 has a structure in which the signal transmission cores 3A and the grounding cores 3B are built in at a predetermined pitch. The most popular data of such a structure are as follows.

Flat insulation sheath: Fluoro resin (PTFE, FEP, ETFE) Cable thickness D: 0.7mm Signal transmission core: 0.16mm silver plated soft copper wire Aers core wire: 0.16mm silver plated soft copper wire core wire Large pitch between: Pa: 2.54 mm Small pitch between cores: Pb: 0.9 mm Propagation delay time: 4.17 nS / m [Problems to be solved by the invention] At present, in a large computer, the processing time is shortened,
To increase the capacity, it is necessary to speed up the signal cable (flat cable) around the central processing unit (CPU), but the propagation delay time of the conventional general flat cable 1 is 4.17 nS / m as described above. Therefore, it is desired to reduce the propagation delay time. When the flat insulating sheath 2 is formed of a foam material, the propagation delay time can be shortened to about 3.8 to 3.7 nS / m, but it is difficult to stabilize the foaming rate with the foam material.
There was a problem that it was difficult to manufacture a stable product because the foaming rate changed during the manufacturing.

An object of the present invention is to provide a flat cable having a structure capable of shortening a propagation delay time and easily manufacturing a product of stable quality.

[Means for Solving the Problems] The structure of the present invention for achieving the above object will be described with reference to FIGS. 1 and 10 corresponding to the embodiment. In the flat cable in which the core wires 3A and 3B are built in at a predetermined pitch, the core wires 3A and 3B are arranged along the longitudinal direction in the flat insulating sheath 2 between the adjacent core wires 3A and 3B. It is characterized in that a facing space 4 is provided.

[Operation] When the space 4 oriented along the longitudinal direction of the core wires 3A and 3B is provided in the flat insulating sheath 2 between the adjacent core wires 3A and 3B as described above, the space 4 extends along the longitudinal direction. It becomes an air layer, and the propagation delay time can be shortened. Further, such a space 4 can be stably formed by, for example, extrusion molding and the quality of the product can be stabilized.

Further, the space 4 in the flat insulating sheath 2 is the core wire 3aA.
If the space is oriented in the longitudinal direction, the flat insulating sheath 2 can be formed simultaneously in the manufacturing process of the flat insulating sheath 2 itself without adding another process for providing the space 4, and the cost increase can be avoided.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.
FIG. 1 shows an embodiment of the flat cable 1 according to the present invention. The parts corresponding to those in FIG. 11 described above are designated by the same reference numerals. In this embodiment, in the flat insulating sheath 2 between the adjacent core wires 2A and 2B, a space 4 having a quadrangular cross section is continuously provided along the longitudinal direction of the core wires 3A and 3B. .

Next, the propagation delay time of the flat cable 1 having such a structure will be described. As is conventionally known, the propagation delay time τ of the flat cable 1 is, as shown in (1),
It is determined by the relative permittivity ε ^* of the insulating material between the adjacent core wires 3A and 3B.

Therefore, when the insulating material forming the flat insulating sheath 2 is air, the propagation delay time can be minimized, so that the relative permittivity of the insulating material between the core wires 3A and 3B must be close to the relative permittivity of air. . Flat cable 1 shown in FIG.
In the case of, the relative permittivity ε ^* of the insulating material forming the flat insulating sheath 2 is in the height direction if the height T of the space 4 is about 2P or more compared to the pitch P between the core wires 3A and 3B. Since the influence of the insulator can be ignored, it is determined by the relationship between the width A occupied by the insulator between the core wires 3A and 3B and the width B occupied by the space 4, that is, the air space factor B / (A + B) between adjacent core wires. Will be done. That is, in the case of FIG. 1, when the air space factor B / (A + B) = V between adjacent core wires is set to, for example, 0.6,
As is clear from the relationship diagram between the air space factor [V] between adjacent conductors of the flat cable 1 and the characteristic impedance correction coefficient [K] shown in FIG. 2, when the insulator is PTFE or FEP,
The characteristic impedance correction coefficient is K = 1.15.

on the other hand, However, Zo: Characteristic impedance of flat cable Zin air: Characteristic impedance when medium is air From Eqs. (2) and (3), In equation (4) Substituting the value of to the expression (1), Becomes If T / P is too small, it is affected by the insulators above and below the flat insulating sheath 2 as described above, Is undesirably large. When T / P = 0.5, it is affected by about 40%. Therefore, it is preferable to set T / P = 0.5 or more for the purpose of the present invention.

In Fig. 1, air space factor B / (A + B) between adjacent cores
By making the value closer to 1, the propagation delay time τ can be further shortened.

An example of the dimensional data of each part of the flat cable 1 of this embodiment is shown below.

Pitch between cores P: 0.45mm Spatial width: 0.27mm Spatial height T: 1.0mm Cable thickness D: 1.5mm Insulator width between cores 3A M: 0.25mm Outer diameter of cores 3A, 3B: 0.16 mm The propagation delay time in this case was 3.8 nS / m ± 0.15.

As the insulator forming the flat insulating sheath 2 in the present invention, a hexafluoropropylene copolymer or a perfluoroalkyl vinyl ether copolymer which is flame-retardant and has an excellent dielectric constant ε = 2.1 is preferable.

When a flame retardant layer such as polyvinyl chloride (PVC) is provided on the outer layer of the flat cable 1, the flat insulating sheath 2 may be made of thermoplastic resin such as polyethylene having a small relative dielectric constant.

Next, an example of an apparatus for manufacturing a flat cable having such a special structure will be described. 3 to 9 are shown as an example in the case of manufacturing the three-core flat cable 1 as shown in FIG. FIGS. 3 to 9 show examples of the die 5, the nipple 6, and the sizing rolls 7 and 8 used in manufacturing the flat cable 1 having three cores.

In the die 5, three rectangular parallel slits 9, 10 and 11 for passing the three core wires 3B, 3A and 3B and passing the insulator in a rectangular shape and parallel to each other,
Two rectangular sideways slits 12 for passing the insulator in a rectangular shape above and below these slits 9 to 11,
13 and 13 are provided so as to penetrate in the longitudinal direction.
On the outlet side of the die 5, a recess 5A including the slits 9 to 13 is formed so that the extruded insulators can be easily integrated.

The nipple 6 is provided with three through holes 14, 15, 16 for positioning and passing the three core wires 3B, 3A, 3B at the centers of the slits 9 to 11 of the die 5.

The sizing rolls 7 and 8 are slits 9 to 1 of the die 5.
Insulators 2A, 2B, 2C extruded from No. 1 and slit 1
Grooves 7A and 8A for integrating the insulators 2D and 2E extruded from Nos. 2 and 13 into the flat insulating sheath 2 are formed opposite to each other on the outer circumference.

In such a flat cable manufacturing apparatus, the three core wires 3B, 3A, 3B are connected to the die 5 via the nipple 6.
When the insulators 2A to 2E are extruded from the slits 9 to 13 in this state and passed through the sizing rolls 7 and 8, the insulators 2A to 2E are integrated. As shown in FIG. 10, the adjacent core wires 3A, 3B
A three-core flat cable 1 having a space 4 continuously provided in the longitudinal direction is obtained.

By using such an apparatus, a flat cable of the type shown in FIGS. 1 and 10 can be manufactured in one step.

The shape of the space 4 is not limited to a quadrangular cross section, and may be an elliptical shape or the like as long as the height dimension T is larger than the width dimension B.

[Effects of the Invention] As described above, the flat cable according to the present invention has the following excellent effects.

(B) In the flat insulating sheath between the adjacent cores, the spaces oriented in the longitudinal direction of these cores are provided, so this space becomes an air layer oriented in the longitudinal direction, and the propagation delay time is reduced. It can be shortened.

(B) Such a space can be stably formed by, for example, extrusion molding, and the quality of the product can be stabilized to facilitate manufacture.

(C) If the space in the flat insulation sheath is a space oriented along the longitudinal direction of the core wire, the flat insulation course itself does not need to be added in one step to provide the space. There is an advantage that they can be formed at the same time and an increase in cost can be avoided.

[Brief description of drawings]

FIG. 1 is a transverse cross-sectional view of an essential part of an embodiment of a flat cable according to the present invention, and FIG. 2 shows a relationship between an air space factor between adjacent core wires and a characteristic impedance correction coefficient for obtaining a relative dielectric constant. FIG. 4 is a longitudinal sectional view showing the relationship between the die and the nipple of the flat cable manufacturing apparatus of this embodiment.
5 and 5 are a perspective view and a front view of the die used in this embodiment, FIG. 6 is a sectional view taken along line XX of FIG. 5, and FIG. 7 is a perspective view of the nipple used in this embodiment. FIG. 8, FIG. 8 and FIG. 9 are cross-sectional views and side views of the sizing roll used in the flat cable manufacturing apparatus of this embodiment, and FIG. 10 is a flat cable manufactured by the die shown in FIG. FIG. 11 is a transverse sectional view showing an example, and FIG. 11 is a transverse sectional view of a main part of a conventional flat cable. 1 ... flat cable, 2 ... flat insulating sheath,
3A, 3B ... core, 4 ... space.

Claims (1)

[Scope of utility model registration request] 1. A flat cable in which core wires are housed in a flat insulating sheath at a predetermined pitch, and in the flat insulating sheath between the adjacent core wires, there is a direction along the longitudinal direction of the core wires. A flat cable characterized by having a space.